The present invention relates to the recycle of industrial wastes, especially to a process for producing fine rubber powder by using waste rubber.
Vulcanized natural rubber and synthetic rubber (referred to as waste rubber) are polymer elastic materials, which are considered difficult to be recycled. The effective treatment and recycling of waste rubber is beneficial to protection of ecological environment and for saving of natural resources.
One of the methods for recycling waste rubber is to make it into rubber powder, which can be mixed into raw rubber materials to replace part of rude rubber. If fine rubber powder is used with a proper proportion in the materials, the shrinkage and ductility of the rubber materials as well as some properties of the rubber product can be improved. Rubber powder can be also used as an additive of building materials. In practice, the particle size of the rubber powder for the above applications is less than 180 xcexcm, which is referred to as a fine rubber powder.
At present, the industrial process for producing the rubber powder is a method of the ambient temperature pulverization and a method of the freezing pulverization. The former is conducted by means of shearing and cutting force of rollers to pulverize waste rubber. The size of most of resultant rubber powders is of 300 xcexcm-600 xcexcm, and that of 180 xcexcm, less than 5%. Although such rubber powder has a burry surface, which is beneficial to its combination with other materials, the amount of the rubber powder in use has to be reduced because the larger size of the rubber powder reduces its function in practical use. In the latter method, the rubber powder obtained by the former method is tenderized at a freezing temperature before being continuously sheared and cut. Such method can produce rubber powders at a size of 250-500 xcexcm, and those at a size of below 180 xcexcm of around 20%. In addition, the smooth surface of such rubber powder makes it difficult combine with other materials. Both the above-mentioned methods have the disadvantages of high assumption of energy, a high investment, a low yield of fine rubber powder and high costs of production.
The present invention provides a method for producing fine rubber powders at ambient temperature so as to overcome the above-mentioned technical drawbacks in the prior art.
A process according to the present invention comprises:
a) pre-pulverizing waste rubber into particles with a size of 1-4 mm;
b) soaking the particles in a solvent selected from one or more alcohols and ethers; and
c) pulverizing the soaked rubber particles into rubber powders with a size of less than 180 xcexcm.
With the process in the present invention, fine rubber powders with a size of less than 180 xcexcm can be produced at ambient temperature at a yield of 100%.